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Commit 0bc6d90b authored by Baruch Even's avatar Baruch Even Committed by David S. Miller
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[TCP] H-TCP: Account for delayed-ACKs 



Account for delayed-ACKs in H-TCP.

Delayed-ACKs cause H-TCP to be less aggressive than its design calls
for. It is especially true when the receiver is a Linux machine where
the average delayed ack is over 3 packets with values of 7 not unheard
of.

Signed-off-By: default avatarBaruch Even <baruch@ev-en.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c33ad6e4

net/ipv4/tcp_htcp.c

+18 −8
Original line number Diff line number Diff line
@@ -29,7 +29,8 @@ struct htcp { 
	u8	modeswitch;     /* Delay modeswitch until we had at least one congestion event */

	u8	ccount;		/* Number of RTTs since last congestion event */

	u8	undo_ccount;

	u16	packetcount;

	u16	pkts_acked;

	u32	packetcount;

	u32	minRTT;

	u32	maxRTT;

	u32	snd_cwnd_cnt2;
@@ -92,6 +93,12 @@ static void measure_achieved_throughput(struct sock *sk, u32 pkts_acked) 
	struct htcp *ca = inet_csk_ca(sk);

	u32 now = tcp_time_stamp;



	if (icsk->icsk_ca_state == TCP_CA_Open)

		ca->pkts_acked = pkts_acked;



	if (!use_bandwidth_switch)

		return;



	/* achieved throughput calculations */

	if (icsk->icsk_ca_state != TCP_CA_Open &&

	    icsk->icsk_ca_state != TCP_CA_Disorder) {
@@ -217,20 +224,24 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt, 
		measure_rtt(sk);



		/* keep track of number of round-trip times since last backoff event */

		if (ca->snd_cwnd_cnt2++ > tp->snd_cwnd) {

		if (ca->snd_cwnd_cnt2 >= tp->snd_cwnd) {

			ca->ccount++;

			ca->snd_cwnd_cnt2 = 0;

			ca->snd_cwnd_cnt2 -= tp->snd_cwnd;

			htcp_alpha_update(ca);

		}

		} else

			ca->snd_cwnd_cnt2 += ca->pkts_acked;



		/* In dangerous area, increase slowly.

		 * In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd

		 */

		if ((tp->snd_cwnd_cnt++ * ca->alpha)>>7 >= tp->snd_cwnd) {

		if ((tp->snd_cwnd_cnt * ca->alpha)>>7 >= tp->snd_cwnd) {

			if (tp->snd_cwnd < tp->snd_cwnd_clamp)

				tp->snd_cwnd++;

			tp->snd_cwnd_cnt = 0;

		}

		} else

			tp->snd_cwnd_cnt += ca->pkts_acked;



		ca->pkts_acked = 1;

	}

}
@@ -249,6 +260,7 @@ static void htcp_init(struct sock *sk) 
	memset(ca, 0, sizeof(struct htcp));

	ca->alpha = ALPHA_BASE;

	ca->beta = BETA_MIN;

	ca->pkts_acked = 1;

}



static void htcp_state(struct sock *sk, u8 new_state)
@@ -278,8 +290,6 @@ static int __init htcp_register(void) 
{

	BUG_ON(sizeof(struct htcp) > ICSK_CA_PRIV_SIZE);

	BUILD_BUG_ON(BETA_MIN >= BETA_MAX);

	if (!use_bandwidth_switch)

		htcp.pkts_acked = NULL;

	return tcp_register_congestion_control(&htcp);

}